Transcript for Why the Pilot Was Locked Out of the Cockpit in Germanwings Crash

So many questions about that co-pilot, and about that cockpit door. The secret combination that should have opened it. How was the captain kept out? ABC's Matt Gutman tonight takes us inside the airbus 320. Reporter: Two inches of bulletproof kevlar. The last barrier against terrorists. Built to withstand even the blast of a grenade. Cockpit doors are designed to keep people out. This is a huge change since 9/11, because prior to that time, accessing the cockpit door was not that difficult. Reporter: But on this flight, it was impossible. We know the captain could be heard on the voice recorder smashing at the door, pleading to be let in. Repeatedly identifying himself. He should have been able to gain access by keying in a simple security code. As this demonstration video from an airbus a-320 shows. But with the alarm buzzing, the person in the cockpit has 30 seconds to flip this switch to lock and keep the door shut. Lubitz may have done just that and could have done so more than once. And the horrifying truth, that door worked exactly as designed. It was impenetrable. What is changing tonight, are regulations abroad. Major international carriers now matching U.S. Policy. Two in the cockpit at all times. David? Matt Gutman, thank you. I want to bring in ABC aviation consultant John nance. And John, when it comes to the cockpit door, we heard the air line today say about the combination lock, that even if the seven-digit code is entered from outside the cockpit, a pilot inside can block entry for up to five minutes. And a lot of people are going say here that a captain should have a way in, no matter what. Well, I think we may need to rethink this. As a matter of fact, I'm sure we need to. It was done for a really good logic, and that was if a pilot is up there and somebody is making an assault on the door and they've got the combination, still need to keep them out. But with, in light of what has happened here, I think we're going to have to take another look at this. A flight attendant will go into the cockpit, so, you always have two people, or you'll see flight attendants block the front with their cart and leave the cockpit door open if the pilot comes out to use the restroom or otherwise. These are the two options you usually see here? And those two options have been working. One of the reasons why, you don't close the door if you have less than two people in there and I think that no alone zone concept is something that needs to be universal. We need to do this all over the planet. And John, we talked about this before. What about cameras in the cockpit? They are every place else these days. Would they help? Absolutely they're going to help, David. We've got to stop this business of trying to guess what happened just by listening to the voice tape. The objections from pilots, that's invading our privacy, is really nonsense at this point. John nance, thank you. We will have much more tonight

This transcript has been automatically generated and may not be 100% accurate.

Now Playing: The Surprising Details About Cockpit Security

Now Playing: Teen hockey player skates after brain injury: 'I feel like the old me'

Now Playing: At least 5 people killed in their cars as fire rips through town

Now Playing: {{itm.title}}

{"id":29939032,"title":"Why the Pilot Was Locked Out of the Cockpit in Germanwings Crash ","duration":"2:45","description":"The cockpit door could be entered by the pilot with a code, but it could also be locked-out from the inside.","url":"/WNT/video/pilot-locked-cockpit-germanwings-crash-29939032","section":"WNT","mediaType":"default"}